I tend to agree with this more optimistic viewpoint on the resilience and adaptability of kids, but do we have any evidence on how this impacts on a whole group of kids rather than individuals? I guess there must be some examples of communities where schools have been destroyed in natural disasters or schools have disappeared in crumbling economies, but I haven't read anything about the outcomes. It's just not the kind of thing you want to be conducting a population-wide experiment on. And while there's still a lot about child psychology that's more myth than robust science, we do have good reason to believe that kids absorb different levels and kinds of information at different times, so if you miss out on certain pivotal moments, you can't just replace it like-for-like.
There are multiple people in this thread that have said they missed out on significant chunks of school and were able to adapt to that without much issue, but it's possible you were just wired the right way to deal with it. What if you're the exception? Alternatively, what if it is true that the majority of kids can adapt to it, but there's a large minority that really can't handle it and suffer long-term consequences? It's the fear of the long-term damage that does justify some caution, I think. We know that people have coped with the social disconnection and changing life priorities differently during this period, and some adults have found it much more difficult than others. No reason to believe that wouldn't apply to kids too. Only they'll have less understanding of what's happening, how to deal with it, or how to communicate it. If you're the government that consciously made a decision to leave those kids behind, how will you feel about it in 10 years when they're suffering all kinds of problems?
I think when faced with that kind of responsibility and potential risks, it's natural to freeze up and just try to continue with things as normally as possible for as long as possible.